Furnace sealing door

ABSTRACT

A sealing door for heat-treating furnaces having a piston and cylinder arrangement that not only raises and lowers the door but also moves the door outwardly slightly upon opening to protect the door seal during the vertical movement of the door and also presses the door against the furnace upon closure to seal the furnace against leakage of internal vacuum or pressure.

United States Patent Harold E. Mescher Pico Rivera, Calif. 840,433

July 1969 Jan. 12, 1971 Pacific Scientific Company Commerce, Calif.

a corporation of California [72] Inventor Appl. No; Filed Patented Assignee FURNACE SEALING DOOR 6 Claims, 10 Drawing Figs.

US. Cl

Int. Cl. F 23111 7/00 Field of Search 1 10/ 1 76, 177; 126/192; 49/209, 210

[56] I References Cited UNITED STATES PATENTS 2,827,864 3/1958 Osterman et al 110/177 3,298,546 1/l967 Jones 110/177X 2,910,022 10/1959 Tinker 110/176 Primary Examiner-Edward G; Favors i I Attorney-Paul B. Hunter ABSTRACT: A sealing door for heat-treating furnaces having a piston and cylinder arrangement that not only raises and lowers the door but also moves the door outwardly slightly upon opening to protect the door seal during the vertical movement of the door and also presses the door against the furnace upon closure to seal the furnace against leakage of internal vacuum or pressure.

PUATEINTED 1 2 m SHEU 2 BF 5 INVENTOR.

il I l ll Harold E. Mescher BY M m Attorney mammals" 3. 554144 sum s or 5 l3 if. 1!.

a 5 16 I7 a 4 F g I 9 '2 'INVENTOR. 7 =8 Harold E. Mescher am m Attorney unequal heating.

' both vacuum andpositive-pressureswere. involved were generally hinged atthe-side and ma'nuailyclampe'd or bolted and manuallyfopened, which necessitated not only considerable free floor spacelin front of the furhace to accommodate the moving door, but also required considerable time for opening and closing the door due -to;the manual work of operating the clamps. Other types-of v prior doors included overhead trolleyrails together with manually clamped or 'bolted-andrnanually opened doors whichrequire considerable time and efi'ort'to use: other doors were .of the autoclave type, with articulated hinging and. either manual or powered rotating seal clamp rings, and were manuallyopened. When the dooris usedas a hot vacuum gate valve, the common design FIG. 8 is a view similar to FIG; 7, showing the door just as it is about to be raised into opened position;

FIG. 9 is an enlarged sectional view of the structure encircled in FIG. 4; and

l. a Y Similar characters of reference are used in the above figures to designate corresponding parts.

" Referring now to the drawings, the reference numeral 2 designates a heattreating furnace-easing shown as of substantially cylindrical shape and havinga sealed outwardly dished rear end wall 2, and the novel door 3 of this invention closing theopen front thereof, the furnace l being'shown supported upon a frame 4. The door 3 is "outwardly dished, as especially shown in FIG. 4 for withstanding pressures, and is provided with a peripheral flanges that is welded to a relatively heavy has been-muse fullwater cooling of the entire door or gate,

and this has been expensive and difficult to maintain, particularly as to temperatures desired. a v v The principal 'objectof theipres'ent invention is to provide a novel vertically rising doorto conserve floor space and that is mechanized}to"1be compatible with automatic-cycling and capable of directly facing a hot chamber without distortion, seal failure; or excessive heat loss,..regardles S 59f vacuum or pressure conditions withintheffurhaee: itself.

A feature of the'inv'ention is to providea novel vertically rising furnace, doorthat israised and lowered by use of pneusteel ring or flange 60f substantially rectangular'cross section. The flange 6 is provided with'an internal annular groove for accommodating a retainirig ring or washer 7 (see also FIG. 9) that retains a disc-shapedplate 8, of heat-resistant alloy that is preferably reinforced 'at' its inner side, to support insulation 9 within the door 3,-the outer surface of the insulation 9 being retained in place by a corrugated disc] 10 carried at its matic cylinders with pistons movable therein, the said pistons and cylinders, not only-serving to raisearid lowerthe door but also serving to apply positive sealing pressure to the door when the same iselosed; thus greatlyijsimplifyingzthe operatorslabors as well asiconsiderably. reducing the cost of con{ struction. Q a r Another feature. of the present invention is to provide a door that is elevated wheri;open', jthus greatly reducing any chance of accidental damage to ,the 'seal of the door. which is great saving-in, floorv space requirements asextra space is' not required for door motion (such as is necessary for swinging doors).

Another feature of the present invention is to provide water-cooling channels ing the door nandabuttingfurnace flange without the necessity of cooling the entire door, the said coolin ehannels' being"'cleanable, which greatly extends the service: life of the equipmentin adverse conditions where untreated water is used forcooling, I

Still another feature of thepresent invention is to provide a furnace door of the above character that "incorporates insulated constructionfor reducingheat loss to a small fraction of that permitted bythe usual water-cooled vacuum gate door or valve, the said door having its -'surface facing the heat so fabricated-as to accommodate differential expansion due to carried thereby, the elevated door when-opened providing a .ing from variable heating of the furnace itself.

The inner face of the flange 6 of the door is highly finished and provided with an annular keystdne-shaped groove 11 for receiving a sealing O-ring 12 that is adapted to abut the highly finished and smooth surface of a-complementary heavy casing ring or flange 13 fixed upon the'jfu'rnace"casingZ. With the door 3 closed, as shownin FIGSQ4-3l1df9 for example, the O- ring 12 serves to seal'the two rings 6 and I3 against the ingress and egress of gases, thus enabling t'hefumace casing 2 to be held at a high internal l vacuum or at a desired pressure therewithin. Since the furnace in operation is hot, in order not to injure the O-ring 12 or highly polished abutting surfaces of rings 6 and 13, these rings are provided with annular grooves l4 through which water is circulated as through entrance and exit passagesIS. Since the cooling water may not be clean, the grooves 14 are shown closed by elastic rings 16, such as 0- rings, which in turn are retained in place by metallic bands 17. By removing the bands 17, the elastic rings 16 can be removed and the passages 14 cleaned at will,

The door 3 is provided at its sides'with upper and lower rollers 18 and 19, the rollers'l8 being rotatably supported on the door 3 substantiallymidway of the height thereof, while the lower rollers 19 are rotatably supported on brackets 20 projecting outwardly from the lower portion of the door. The two upper rollers 18 of the door slidably engage in grooves 21 provided in the vertically extending sides '22 of a hollow rectangular door frame structure 23. Likewise, the lower rollers 19 of the door 3 are adapted to slidably engage in grooves 24 provided in the sides 22 ofthe door frame structure 23. This door frame structure serves to guide the 'doorin its vertical travel,

Other features and advantages of thepresentinvention will become apparent after a perusal of the following specification take in connection with the accompanying drawings wherein:

' FIG. 1 shows'a front elevation 'a furnace equipped with the."

novel fumace-sealing door of this inventiom'the door being shown in closed position; 1 1

'FIG. 2 is-a viewtaken along line 2-2 of FIG. 1;

FIG. 3 is a partial sectional view taken substantially along line 3-3 of FIG. 1',

and this frame is pivotally supported at its upper portion upon pivot pins 25 carried by'brackets 28 attached to the fumace casing 2, so that the door frame structure can pivot about the pins 25, as will further appear. The lower portion of the door frame structure is formed with rearwardly directed vertically slotted projections 26 at its sides through which pivot pins 27 slidingly extend, which pins are carriedby bell crank levers 29 FIG. 4 is a partial sectional view takensubstantially along the line 4-4 ofFIG. 1; v I a FIG. 5 is a partial sectional view taken substantially along the line 5-5 of-FIG. l;

FIG. 6 is an enlarged fragmentary viewofa portion of the structure of FIG. 1, with parts'broken away;

FIG. 7 is a fragmentary side elevation view of the furnace door'and associatedstructure, showing the door in closed a position;

that are'pivoted by pins 30 upon brackets 31 fixed on the furnace frame 4.

The forward free ends of .bellcrank levers 29 are pivotally connected by pins 32 to the lower ends of pneumatic cylinders 33 positioned at the sides of the door 3 and extending substantially vertically, said cylinders being supported by the levers 29. As especially shown in'FIG. 6, the rods 34 of pistons 35 I. movable within cylinders 33 are connected at their upper ends by pivot pins'41 exteriorly of the cylinders to brackets 36 attached to the door 3 for supporting the latter. The two cylinders 33 (see FIGS. 1 and 2) are connected adjacent their FIG. 10' is an enlarged view taken along line 10-10 of F IG.-

upper and lower ends by compressed air lines 37 and 38 to a four-way control valve 39 which serves to supply pressure fluid such as compressed air at desired selected pressures to the upper and lower ends of the cylinders 33. The rear arms of the bellcrank levers 29 are provided with screw stops 40 which in use serve to limit the outward swinging movement of the door 3 when the same is opened, as will further appear.

With the door in closed position, as shown in FIGS. 3, 4, 5 and 7, for example, the forward arms of the bellcrank levers 29 are inclined upwardly somewhat while the rear arms carrying the adjustable 40 are in a rear position, causing the pivot pins 27, acting through projections 26, to hold the door frame member in its rearmost position with the door 3 tightly abutting the furnace door ring 13 in sealed relation. It will be noted that in this position of the door the lower rollers 19 are positioned opposite a flared lower opening in the guide 24 of the door frame structure, whereas the rollers 18 rest upon stop members 42 positioned at the lower end of the grooves 21, so that the weight of the door is carried on rollers 18 at this time resting upon stop members 42, which permits the door to pivot somewhat and adjust itself so that its flange 6 completely abuts the flange 13 of the furnace casing.

When it is desired to open and raise the door, compressed air from four-way control valve 39 is supplied to the lower ends of cylinders 33 through conduit 38. However, at first, the weight of the door tends to retain the same in closed position. The pressure between the lower sides of the pistons 35 and the lower ends of the cylinders 33 applied to pivot pins 32 and 41, as indicated by the arrows in FIG. 8, will cause the cylinders to move downwardly somewhat, turning bellcrank levers 29 counterclockwise from the position shown in FIGS. 3, 4, and 7, for example, to the position shown in FIG. 8 wherein the forward arms of the bellcrank levers are depressed somewhat to a substantially horizontal position and the rear arms are moved forwardly until the stops 40 abut the door frame. This motion of the bellcrank levers causes supporting pins 27 to move the lower end of the door frame structure outwardly, as shown in FIG. 8, to produce a space between the ring members 6 and 13, bearing in mind that the upper side portions of the door frame structure are turnable on pivots carried by the furnace. When the adjustable stops 40 contact the door frame, the pivoting motion of the levers 29 ceases, and the pneumatic pressure within the lower portions of the cylinders will then act to raise the pistons 35 and piston rods 34, thus acting through pivot pins 41 to raise the door with the rollers 18 and 19 riding in their respective guide grooves 21 and 24 until the pistons 35 reach the top of their respective cylinders, in which position the door is fully opened. The door frame structure is preferably inclined slightly forwardly extending from its lower to its upper portion so that as the door rises it will separate the flange rings 6 and 13 to a greater extent throughout their lengths to prevent injury to the O-ring 12 when the door moves upwardly.

To close the door, compressed air is supplied to the upper 81 of the cylinders 33 through conduit 37 while maintaining sufficient pressure in conduit 38 to obtain the desired rate of downward movement of the door. Since the weight of the door, acting through pins 32 on bellcrank levers 29, still retains these levers in their downward-turned positions (as shown in FIG. 8) clearance is provided between the sealing ring 11 and the furnace ring 13 so that no injury takes place during this closing movement of the door.

Finally, the upper guide rollers 18 of the door reach their stops 42 in the frame 22 before the cylinders 33 are fully retracted, at which time the door and cylinder flanges are in horizontal alignment, Continued pressure supplied by conduit 37 as applied to pivot pins 32 and 41, as shown by the arrows in FIG. 7, will now force cylinders 33 upwardly somewhat since pistons 35 can move no lower, being stopped by the downward limit of the door movement. This will cause the cylinders 33 to pull upwardly on bellcrank levers 29 so that these levers move from their positions shown in FIG. 8 to their positions shown in FIG. for example, causing the rear arm of the bellcrank levers to turn clockwise so that stops 40 disengage the frame and move rearwardly, thereby moving pins 27 rearwardly and forcing the door flange 6 into tight contact with furnace casing flange 13, resulting in sealing of these two flanges by seal 12. The door floats into its sealed position since the two lower guide rollers 19 are now positioned opposite the flared portions of their guides 24 and can move outwardly slightly if necessary to accomplish the floating action of the door about rollers 18 and resulting in firm uniform seating of the seal 12 completely around the door opening, thus effectively sealing the door to the furnace. It will be noted that since pivot pins 27 are closer to supporting pin 30than pins 32 are to this pin, the pressure ofthe cylinders obtain a mechanical advantage, firmly pressing the door against the furnace. Even after the two flanges 6 and 13 are in full engagement, the cylinders 33 are not completely retracted, so that these cylinders apply a force on the door amplified by the mechanical advantage of the levers 29 to effectively clamp the door, making possible sealing against both positive and vacuum pressures within the furnace.

Since many changes could be made in the above construction and many apparently sidely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a heat-treating furnace having a casing with a door opening provided with a casing flange surrounding such opening, a vertically moving door provided with a complementary flange having a sealing gasket adapted for abutting the furnace flange to seal the furnace in use, a door frame structure surrounding and guiding said door in its vertical movement, the upper portion of said door frame structure being pivotally supported upon the furnace, bellcrank levers pivotally supported upon the lower portion of the furnace and having the first of their two arms slidingly and pivotally connected to the lower portion of said door frame structure, and actuating cylinders with internal pistons, said cylinders being pivotally connected at their lower ends to the second of the arms of said bellcrank levers, said pistons extending upwardly and having upwardly extending piston rods projecting outwardly of said cylinders and pivotally connected to said door for raising and lowering the same, said actuating cylinders and pistons acting in conjunction with the weight of the door when opening the latter to actuate said bellcrank levers upon the supply of pressure fluid to the lower portion of said cylinders to move said door frame structure outwardly somewhat away from the furnace, thereby freeing said door sealing gasket from the casing flange so that the continued supply of pressure fluid effecting raising of the door will not injure said door sealing gasket.

2. In a heat-treating furnace as defined in claim 1 comprising stop members carried by the first-named arms of said bellcrank levers to limit the outward movement of the door frame structure and hence of the door, the first-named bellcrank lever arms connected to said door frame structure being shorter than the second-named arms supporting said cylinders and pistons, the closing of the door effected by supplying pres sure fluid to the upper end portions of said cylinders to depress said pistons serving to move the door downwardly at a controlled rate depending upon the pressure of the cushioning fluid below said pistons, the pressure fluid above said pistons acting upon the termination of the downward movement of the door to force said cylinders upwardly somewhat and actuate said bellcrank levers to move the door against the furnace casing, the mechanical advantage provided by the first-named shorter arms of said bellcrank levers serving to force said door flange-sealing gasket tightly against the furnace casing flange, thereby sealing the furnace against both vacuum and positive internal fluid pressures.

3. In a heat-treating furnace as defined in claim 2 comprising roller guides for guiding the door provided in said door frame structure, a pair of upper rollers positioned substantially at the midheight of the door for guiding the lattei" in one of said roller guides, and a pair of lower rollers positioned substantially at the bottom-of the door for movement in another of said roller guides,'and stop members fixed in a said upper roller guides for limiting the'downwardmovement of the door so that the flange thereof is opposite said fumace flange when the door is in its lowest position. 1

4. In a heat-treating furnace as defined in claim 3 comprising outwardly flared extensions provided on said lower roller guides, said extensions enabling slight outward movement of said lower rollers permitting the door to rock slightly on its upper rollers when the. door is closed, to thereby effect uniform sealing pressure all around the door flange.

5. In a heat-treating furnace as defined in claim 4 wherein said door isprovided on its inner wall with a heat-resistant 6 disc-shaped plate to resist the furnace heat, insulation in front of said plate, and a second disc-shaped plate in front of said in- I sulation to aid in retaining the latterin place, said door having a retaining ring for retaining a said heat-resistant disc-shaped plate in place while allowing for thermal expansion and contraction of the same.

6. In a heat-treating furnace as defined in claim 5 wherei said furnace casing flange and said complementary doo flange are formed with annular, open cooling water-circulating grooves for protecting said door-scaling gasket against heat injury in use, removable elastic rings normally closing said grooves, whereby the removing of said rings permits the cleaning of said grooves, and metallic bands for normally retaining said elastic rings in place. 7 

1. In a heat-treating furnace having a casing with a door opening provided with a casing flange surrounding such opening, a vertically moving door provided with a complementary flange having a sealing gasket adapted for abutting the furnace flange to seal the furnace in use, a door frame structure surrounding and guiding said door in its vertical movement, the upper portion of said door frame structure being pivotally supported upon the furnace, bellcrank levers pivotally supported upon the lower portion of the furnace and having the first of their two arms slidingly and pivotally connected to the lower portion of said door frame structure, and actuating cylinders with internal pistons, said cylinders being pivotally connected at their lower ends to the second of the arms of said bellcrank levers, said pistons extending upwardly and having upwardly extending piston rods projecting outwardly of said cylinders and pivotally connected to said door for raising and lowering the same, said actuating cylinders and pistons acting in conjunction with the weight of the door when opening the latter to actuate said bellcrank levers upon the supply of pressure fluid to the lower portion of said cylinders to move said door frame structure outwardly somewhat away from the furnace, thereby freeing said door sealing gasket from the casing flange so that the continued supply of pressure fluid effecting raising of the door will not injure said door sealing gasket.
 2. In a heat-treating furnace as defined in claim 1 comprising stop members carried by the first-named arms of said bellcrank levers to limit the outward movement of the door frame structure and hence of the door, the first-named bellcrank lever arms connected to said door frame structure being shorter than the second-named arms supporting said cylinders and pistons, the closing of the door effected by supplying pressure fluid to the upper end portions of said cylinders to depress said pistons serving to move the door downwardly at a controlled rate depending upon the pressure of the cushioning fluid below said pistons, the pressure fluid above said pistons acting upon the termination of the downward movement of the door to force said cylinders upwardly somewhat and actuate said bellcrank levers to move the door against the furnace casing, the mechanical advantage provided by the first-named shorter arms of said bellcrank levers serving to force said door flange-sealing gasket tightly against the furnace casing flange, thereby sealing the furnace against both vacuum and positive internal fluid pressures.
 3. In a heat-treating furnace as defined in claim 2 comprising roller guides for guiding the door provided in said door frame structure, a pair of upper rollers positioned substantially at the midheight of the door for guiding the latter in one of said roller guides, and a pair of lower rollers positioned substantially at the bottom of the door for movement in another of said roller guides, and stop members fixed in a said upper roller guides for limiting the downward movement of the door so that the flange thereof is opposite said furnace flange when the door is in its lowest position.
 4. In a heat-treating furnace as defined in claim 3 comprising outwardly flared extensions provided on said lower roller guides, said extensions enabling slight outward movement of said lower rollers permitting the door to rock slightly on its upper rollers when the door is closed, to thereby effect uniform sealing pressure all around the door flange.
 5. In a heat-treating furnace as defined in claim 4 wherein said door is provided on its inner wall with a heat-resistant disc-shaped plate to resist the furnace heat, insulation in front of said plate, and a second disc-shaped plate in front of said insulation to aid in retaining the latter in place, said door having a retaining ring for retaining a said heat-resistant disc-shaped plate in place while allowing for thermal expansion and contraction of the same.
 6. In a heat-treating furnace as defined in claim 5 wherein said furnace casing flange and said complementary door flange are formed with annular, open cooling water-circulating grooves for protecting said door-sealing gasket against heat injury in use, removable elastic rings normally closing said grooves, whereby the removing of said rings permits the cleaning of said grooves, and metallic bands for normally retaining said elastic rings in place. 